This is working for me when I tried to use bootstrap CSS with DTE.
/code/
DescEditor.on('open', function () {
//DescEditor.show(); //Shows all fields
$('#DTE_Field_City').prop('readonly', true)
$('Div.DTE_Field_InputControl input').addClass('form-control');
$('Div.DTE_Field_InputControl select').addClass('form-control');
});
/code/

I still don't know how to align 2 fields in the same row (input-group, input-group-addon).